Abstract No. 389 Characterization of Venous Blood Flow with Computational Models: Effects of Stent Placement and Gravity

To characterize vein wall deformation and luminal flow changes due to mural biomechanics, stent placement, and gravity. Inflow-stent mismatch and recirculation zones following stent placement may undermine patency rates. Prior computational models investigated the effects of vein wall biomechanics and low inflow without consideration of gravity. This study expands on prior work by simulating the effects of gravity and a range of inflow velocities before and after stent placement in healthy vs post-thrombotic (diseased) veins. A computational modeling software (ADINA, Bentley Systems, Inc) was used to create eight fluid-structure interaction models of iliac veins in various conditions (healthy vs diseased, stented vs unstented, and with or without gravity (opposing the direction of flow). Vein wall properties were from established models. Stent placement was simulated as a fixed increase in vein diameter (16.7%) in the mid-segment of the vein. In all models, steady-state results were calculated for inflow velocities between 0–80 cm/s. In both healthy and post-thrombotic veins, the mismatch in diameter between the stented segment and the adjacent unstented segment created a region of abnormal flow recirculation within the stented vein. Increases in inflow-stent diameter mismatch correlated with larger recirculation zones. Increases in blood flow velocity and the inclusion of gravity opposite to the direction of flow both resulted in decreased inflow-stent diameter mismatch (due to increase pressure gradients), and thus decreased recirculation zones. Effects were more pronounced in diseased veins compared to healthy veins. Under similar conditions, post-thrombotic veins exhibited larger recirculation mismatch and a more heterogeneous recirculation zone in the stented segment. Our results demonstrated that stent placement, vein stiffness, gravity, and inflow velocity are important biomechanical variables affecting recirculation regions. Future studies will determine the relative impact of these phenomena to better understand the modest patency rates of venous stents.